The following description relates to an energy management system (EMS) and a control method using the same, and more particularly to an energy management system (EMS) and a control method using the same, capable of determining an operation mode of a high voltage direct current (HVDC) using system information inputted from the EMS via a network.
There may be two types of power channel coupling methods in which one type is to be coupled with an existing alternating current (AC) power system to one or more loads such as, but are not limited to, household appliances and other energy consuming devices without use of intermediate components, and the other is to be coupled with a power system to loads by converting an alternating current (AC) to a direct current (DC) using an AC-DC converter. Herein, the phrase “coupled with” is defined to mean directly connected to or indirectly connected with through one or more intermediate components. Such intermediate components may include both hardware and software based components.
Recently, interests have increased on the method of coupling the power channel to loads using the AC-DC converter instead of the method dispensing with an intermediate component. This is because the method using the AC-DC converter has an advantage in terms of cost when the power is supposed to be transmitted to a long distance location. Furthermore, the method using the AC-DC converter is capable of transmitting a large capacity of power without affecting the AC power system, and is connectible to other systems of different frequencies. Meanwhile, a high voltage direct current (HVDC) system using an AC-DC converter has been locally set up here in Korea between a southern town known as Haenam and a southernmost Jaeju island.
FIG. 1 is a schematic block diagram illustrating a high voltage direct current (HVDC) system that connects a power channel between two local areas.
Referring to FIG. 1, the HVDC system may comprise: a first transformer 110 connected to an AC bus line 100 of a first area and a second transformer 112; a first converter unit 120 converting an AC inputted from the first transformer 110 and the second transformer 112 to a DC and a second converter unit 122; a first inverter unit 124 and a second inverter unit 126 that convert DC to AC; a third transformer 114 and a fourth transformer 116 that convert the voltage of the AC converted by the first and second inverter unit 124 and 126, and are connected to an AC bus line 101 of a second area; a first DC line 102 connecting the first converter unit 120 to the first inverter unit 124 and a second DC line 103 connecting the second converter unit 122 to the second inverter unit 126; a total of 18 circuit breakers 131˜148 for protecting each constituent element comprising a system and the high voltage direct current system; and a first bypass line 104 and second bypass line 105 for transmitting the power detouring an accident section during an accident. The first converter unit 120 and the second converter unit 122 may include four converters, and the first and second inverter unit 124 and 126 may include four inverters.
Meanwhile, the HVDC system needs an effective power supply that is stable in response to a system status, the function of which is performed by an energy management system (EMS). That is, the EMS is an automatic control system capable of collecting data of nation-wide power stations and major substations for production of economic electric power and provision of the power to loads, whereby a power system network can be generally controlled and loads can be effectively distributed.
The EMS now analyzes a system based on actual operation information of the HVDC system. The actual operation information of the HVDC system may be obtained by an operator of a HVDC substation. To be more specific, a manager of the EMS (hereinafter referred to as EMS manager) may obtain the actual operation information of the HVDC system via communication (e.g., telephone communication) with an HVDC substation operator.
Using the aforementioned method, the EMS can receive the operation information from the EMS operator to generate an electric circuit of HVDC system based on the inputted operation information. A channel is analyzed based on the electric circuit information (i.e., connection information among electrical elements comprising the HVDC system) thus generated to provide an energy management for power control. Furthermore, the electrical circuit of the HVDC system may be displayed on a screen for the EMS operator to view.
For example, the EMS operator obtains normal operation mode information via communication with an HVDC substation operator to input the normal operation mode information to the EMS. The EMS generates the electric circuit of the HVDC system based on the inputted normal operation mode information, as depicted in FIG. 2, and performs the power control by analyzing the system based on the generated electric circuit information.
However, the aforementioned method suffers from a drawback in that erroneous system analysis may be made by mistakes of the operator as the operation information of the HVDC system is acquiesced from the operator, making it difficult to cope with sudden happenings of accidents.
For instance, in a case the HVDC substation operator makes a wrong judgment on an operation mode to send to the EMS operator operation information different from actual operation information, the wrong operation information may be inputted to an EMS application program, and a wrong interpretation of the system may be made, resulting in provision of wrong energy management.
Another drawback is that the EMS manager may not obtain the operation information on the HVDC system due to interrupted communications with the HVDC substation operator, whereby the EMS may fail to perform the power control based on the actual operation mode of the HVDC system.